The X-Men have been defeated and captured by the Sentinels leaving Professor X the only member of the group uncaptured. Having recovered from his failed attempt at trying to shut down Master Mold with his mental powers, Xavier witnesses the Sentinel base retract back into the ground, and decides to take a different approach to defeating this robotic menace. Deciding to go back to examine the deactivated robot at the television station, he mentally summons a passerby to pick him up and drive him into the city.

Meanwhile, the X-Men have been imprisoned in a transparent cage, pinned to its surface by artificial gravity. Try as they might, they cannot break free. When Master Mold gets all the information he can from the Beast, he deems the X-Men a paltry threat and orders the Beast be caged with his comrades. When Bolivar Trask asks Master Mold what he intends to do with the X-Men, the robot responds by telling him that he intends to eventually destroy them as per Trask's programming. Having realized the errors of his ways, Trask denounces this but Master Mold is unswayed and threatens to destroy a nearby town if Trask doesn't agree to build more Sentinels.

Back in New York City, the Professor is brought to the television station, where he first encountered the Sentinels, and where one of their numbers still lays inert. Secretly probing the robot with his mental powers before a perplexed police officer, the Professor learns that the Sentinel has a receiver unit much like a television set and that something must have caused interference. Looking out the window, he notices that the cause is a giant crystal on display atop the Crystal Products Building. This gives the Professor just the idea on how to destroy Master Mold and the other Sentinels.

Back at the Sentinel base, the other X-Men feel the artificial gravity of their cell weaken as the Sentinels prepare to put the Beast in the cell with them. Cyclops organizes the X-Men and when a small opening is made in their transparent prison, they attack and break free. The Sentinels are caught off guard and trip over themselves as the X-Men gain the advantage and take out their captors with their mutant powers. The X-Men make a break for it; however, the Sentinels recover and fire their stun beams at the young mutants, knocking them out. They are preparing to kill the X-Men when they suddenly collapse. It is because at that very moment outside, Professor X and the authorities have arrived in three helicopters carrying a giant crystal. Suddenly, the high tech Sentinel base rises out of the ground and a giant cyclone firing cannon begins to attack the helicopters.

Inside, the X-Men revive and are alerted telepathically by the Professor of the Sentinels's weaknesses. Rushing off to face Master Mold, the X-Men are startled when the lights begin to go out as some giant machine beneath their feet begins operating, causing fuses all over the complex to blow. This is because Trask has begun the operations that allow Master Mold to create new Sentinels. Master Mold harnesses powerful electrical energy, channeling it into a device that will construct eight new and more powerful Sentinel robots.

Realizing that with enough power, Master Mold can go on producing Sentinels forever and dominate all mankind, Trask finally decides that he cannot allow such a thing to happen, no matter the cost. Denouncing Master Mold one more time and finding that his life is sacrifice, Trask smashes a vital machine in the lab causing a massive explosion. The X-Men, just in the outside corridor, are rocked by the explosion. The heat from the flames causes Iceman to pass out, prompting Beast to rescue his friend before he gets crushed under falling debris. As the complex is falling down around their heads, the X-Men manage to escape the destruction with the help of Marvel Girl's telekinetic powers.

Outside, there is a close call as Beast carries Iceman out of the complex when the wall begins to crumble. Passing his unconscious comrade to the Angel, Beast quickly runs down the side of the complex by himself just moments before it explodes. Watching the destruction, the X-Men wonder what might have happened down there, completely unaware that Trask had learned the errors of his ways and sacrificed himself in order to save humanity from Sentinel domination.

With the threat of the Sentinels over, the X-Men are unaware that back at their mansion, someone lurks in the shadows waiting for their return to pose as a new threat to the group of mutants.